Coupling device for opposed pistons in free-piston engines



u@ 3f 94- w. KILCHENMANN CQUPLING DEVICE FOR OPPOSED PISTONS IN FREE-PISTON ENGINES- Filed Noi'. so, 194s 4 sheets-sheet 1 mi@ 39 W43- w. KILCHENMANN 2,446,423

CCUPLING DEVICE FOR OPPOSED PISTONS IN FREE-PISTON ENGINES Filed Nov. 30, 1945 4 Sheets-Shea?l 2 nNvEN-ron WAL TER /f/LCHENMAA/N BY A @La-a. GWMM ATTORNEYS Aug 3, 948- w KHLCHENMANN 59423 COUPLING D-EVICE FOR OPPOSED PISTONS IN FREE-PISTON ENGINES l Filed Nov. 50, 1945 4 Sheets-Sheet 3 INVENTOR W41] Ef? /f/l CHfA/MH/VA/ Ug- 3 E943 W. KLLQHENMANN COUPLING DEVICE FOR OPPOSED PISTONS IN FREE-PISTOL! ENGINES Filed Nov. 30, 1945 4 Sheets-Sheet 4 INVENTOR WAL TER /f/ CHEN/vm/VA/ BY QW @M MJM ATTORNEYS Patented Aug. 3, 1948 COUPLING DEVICE FOR OPPOSED PISTONS IN FREE-PISTON ENGINES Walter. Kilchenmann, Winterthur, Switzerland, assignor to Sulzer Freres, Societe Anonyme, Winterthur, Switzerland Application November 30, 1945, Serial No. 632,044

lln Switzerland October 9, 1945 (Cl. 12S- 46) 1o claims. l

The invention relates to a coupling device for opposed pistons in free-piston engines and consists in that two coupling members, each connected to a free piston, are connected by a gear which guides the links connecting the coupling members to the gear almost or entirely in a straight line,

In the drawings a number of embodiments of the invention are shown diagrammatically.

Fig. 1 shows a known coupling device,

Fig. 2 the design of the gear consisting of two rocking levers positively coupled to each other,

Figs. 3 and 4 show a variant of the positive connection of the levers in Fig. 2,

thus of the free pistons 2, 3. The connecting links 8 move in the arcs I2, whose camber is relatively slight, so that the deviations of the coupling rods 5 are small. There is scarcely any reaction on the compressor pistons 3.

Furthermore it is possible to arrange a protective pipe I3 around the coupling rods 5, this pipe being tightly xed against the compressor piston 3 by means of the flange I4 and guided through the oil sealing means I5 in the walls I 6. The walls I6 separate the gear space I from the spaces I8 in the compressor cylinders 3. In the gear space Il oil is sprayed, and the oil scraper rings I9 in the seals I5 prevent the spaces I8 of Figs 5 t0 7 a gear formed by a rocker arm and 15 the compressor cylinders 3 and the power pistons cranks. 2 from being dirtied with gear oil. At the same Figs. 8 and 9 a gear with the connecting links time the consumption of gear oil is kept low. guided in a straight line, and In Figs. 3 and 4 the rocking levers 9, instead Figs. 10 and 11 a variant of Figs. 8 and 9. of the toothed segments I I in Fig. 2, are so con- In known free-piston engines (Fig. 1) there 20 nected by flexible steel bands 20, 2| that positive work in the combustion cylinder I two power pistons 2 which move contrarily to each other and are rigidly connected to the compressor pistons 3 in the compressor cylinders d. In order to ensure the opposed motion of the free pistons 2, 3, a coupling device consisting of coupling members 5 and the rocker arrn 3 is provided.

When the free-piston engines are of short construction the coupling rods 5 cannot be guided by means of a crosshead, but it is necessary to link them up to the compressor pistons 3. The coupling rods 5 are connected to the rocking arm 6 by the connecting link 8.

When the free pistons 2, 3 are inthe end position of their stroke the coupling device comes into an outstretched position in which the rocking arm E lies parallel' to the cylinder I. The rocking arm E is then thrown over on to the other side by its momentum, so that in the next inward stroke the coupling device comes to lie in the position shown by chain-dotted lines. Not only, therefore, is a relatively large angle of deviation a of the coupling rods 5 to be reckoned with, but great forces present themselves in the link pins l and turn the compressor pistons 3 about their axes if only one of the two rocker arms 6 on the two sides of the cylinder I swings Over.

In order to remove these disadvantages two rocking levers 9 are provided in Fig. 2 whose axes of rotation l are arranged outside of the longitudinal axes of the coupling members 5 by the length of the levers 9. These rocking levers 9 have toothed segments il which positively eect ythe opposed motion of the connecting links 8 and coupling is ensured whatever the direction of motion.

The compressor pistons 3 in Fig. 5 draw in air during the inward stroke through several suction valves 22 arranged around the compressor cylinder Il, these valves all being connected to the annular space 23 which is in communication with the surrounding air or with a supply of already compressed air in a manner not shown in the drawing.

The air compressed during the outward stroke of the pistons 3 iiows through delivery valves 24 (Fig. 5) which are also arranged around the compressor cylinder 4 into the annular delivery space 25, which is connected by a conduit 25 to the annular space 26 and the combustion cylinder I, so that in the outer end position of the stroke of the power pistons 2, the compressed air flows into the combustion cylinder I through the ad# mission ports 2l as scavenging and combustion air. When the power piston 2 moves inwards the combustion air in the combustion cylinder I is compressed and at the end of this stroke fuel is injected through one or more fuel valves 28. The combustion gases force the pistons 2 apart and escape through the exhaust ports 2S into the exhaust space 30, which is in communication with the surrounding air or with a power gas consumer according to the employment and the method of working of the free-piston engine.

The coupling members 5 are connected -by a gear. This has a rocker element 3|, which is supported on both sides by means of .the pins 32, and two crankpins'33 around which the cranks 3l! turn, the latter being provided with a toothed wheel 35. The .toothed wheels 315 engage with the stationary toothed rim 36 in such a way `that the connecting links 8, which connect the coupling members 5 to the cranks 34, are guided almost in a straight line, as can be seen from Figs. 6 and 7. The external diameter of the toothed wheels 35 is smaller than the distance between their centres of rotation, the crankpins 33. In .this way the toothed wheels 35 can be arranged in the same plane, as Fig. 5 shows.

In Figs. 8 and 9 the coupling members 5 are screwed tight to the compressor piston 3 and are themselves surrounded by the voil seals i5. For the connecting links 8 are guided in va straight line owing to the fact that the length of the crank 34 is equal to the distance of its centre of rotation from the point of rotation of the rocker element 3i and the pitch circle diameter of the toothed wheels 35 is equal to the distance between their centres of rotation, i. e. between the crankpins 33. For this to be so, however, it is necessary to arrange the toothed wheels 35 in different planes, as shown in Fig. 8.

The movement of the connecting links 8 on a straight line and the rigid connection of the coupling rods 5 to the compressor piston 3, however, are possible without the space for the coupling gear being enlarged (Figs. l0 and l1) if the toothed wheels 35 have teeth so undercut that the addendum circle 3l of the toothed wheels 35 is smaller than the pitch circle 38 of their toothing. Although now .the pitch circle 38 is equal to the distance between the centres of rotation of the toothed wheels 35, it is nevertheless possible to arrange these two wheels 35 in one plane once more. For the play between them necessary for free turning corresponds to the difference between the addendum circle 31 and the pitch circle 38.

Instead of providing the rocker element 3| for guiding the links 8 in a straight line with teeth in order to produce the necessary movement of the cranks 34, this movement can equally well be obtained by means of a flexible steel band and drum gear arranged to operate as the full equivalent to the two gear arrangementsillustrated in Figs. 8-9 and Figs. 10-11. The arrangement of this steel band and drum gear parallels that of the -toothed wheel gear in the same way that the steel band and plane segment gear of Figs. 3-4 parallels the operation ci the toothedv segment gear of Figs. l-2. That is to say, that the ixed sha-ft in the position of the pins 32 would carry rotatably mounted the rocker element 3| and an independently rotatably mounted drum linked by steel bands to two drums of half the diameter mounted on crank pins 33 rigidly affixed to cranks 34. The diametral di'erence between the drums thus secures the same straight line movement with the identical diametral difference between the pitch circles of the stationary toothed rim 36 and the toothed wheels 35 to which the large drum and the twosmall drums are respectively geometrical equivalents.

The parts of the rocker element 3i, the crankpins 33 and the lateral parts are connected up by toothed couplings I9 (Fig. 5), the end faces of the crankpins 33 having .teeth which engage with the teeth of the lateral parts and in which bolts -are provided which pass through these parts and hold them together.

Iclaim:

1. In a free piston engine, the combination including an internal combustion cylinder, two power pistons in said combustion cylinder working opposed to each other, a compressor cylinder arranged at each end of said combustion cylinder, a compressor piston in each of said compressor cylinders attached to the adjacent power piston, a connecting rod pivotally connected to each of said compressor pistons, and gear means linking and pivotally connected to said connecting rods 'arranged to insure Vthe opposed motion of said pistons with only a small angle of devia- .tion of said connecting rods.

2. The combination of claim 1 in which the gear means include two rocking levers whose axes of rotation are arranged outside the longitudinal axes of the connecting rods by approximately the length of said levers and toothed segments positively coupling said levers.

3. The combination oi' claim 1 in which the gear means include a rocker element having crank elements rotatably mounted on the eX- tremities thereof, each of said crank elements including a crank arm proper pivotally connected to one of the connecting rods and a toothed member, and a stationary rack adapted to engage said toothed members to guide the points of connection between said crank arms proper and said connecting rods substantially in a straight line during rotation of said rocker element.

1. The combination of claim 1 in which the gear means include a rocker element having crank elements rotatably mounted on the extremities thereof, each of said crank elements including a crank arm proper pivotally connected to one of the connecting rods and a toothed member, the radius of each of said crank arms y proper being equal to the distance from the center of its pivot on said rocker element to the center of rotation of said rocker element, and a stationary rack adapted to engage said toothed members to guide the points of connection between said crank arms proper and said connecting rods substantially in a straight line during rotation of said rocker element. s

5. The combination of claim 1 in which the gear means include a rocker element having crank elements rotatably mounted on the extremities thereof. each of said crank elements including a crank arm proper pivotally connected to one of the connecting rods and a toothed member, the external diameter of said toothed members being smaller than the distance between the centers of their pivots on said rocker element, and a stationary rack adapted to engage said toothed members to guide vthe points of connection between said crank arms proper and said connecting rods substantially in a straight line during rotation of said rocker element.

6. The combination of claim 1 in which the gear means include a rocker element having crank elements rotatably mounted on the extremities thereof, each ci' said crank elements including a crank arm proper pivotally connected to one of the connecting rods and a toothed member, said toothed members being mounted on said rocker element in different planes and with their pitch circle diameter equal to the distance between the centers of their pivots on said rocker element, and a stationary rack adapted to engage said toothed members to guide the points of connection between said crank arms proper and said connecting rods substantially in a straight line during rotation of said rocker element.

7. 'I'he combination of claim 1 in which the gear means include a rocker element having crank elements rotatably mounted on the extremities thereof, each of said crank elements including a crank arm proper pivotally connected to one of the connecting rods and a toothed member, said toothed members having a pitch circle diameter equal to the distance between the centers of their pivots on said rocker element and having teeth so undercut that the addendum circle is smaller than the pitch circle, and a stationary rack adapted to engage said toothed members to guide the points of connection between said crank arms proper and said connecting rods substantially in a straight line during rotation of said rocker element.

8. The combination of claim 1 including a protective pipe rigidly attached to each of the compressor pistons surrounding the connecting rods and an oil seal engaging and guiding said pipe and closing off the space occupied by the gear means from the compressor cylindera 9. The combination of claim l in which the gear means include a rocker element supported at two points on its axis ci rotation.

10. The combination of claim l in which the gear means include a multi-part rocker element, the separate parts of said element being operably connected by means of toothed couplings.

REFERENCES man Tho following .references are of record in the 10 le of this patent:

Um'ran STATES PATENTS 

